Paratuberculosis is responsible for major economic losses -particularly in the dairy sector- because of reduced milk production in affected animals. As the existing vaccine, composed of whole, killed mycobacteria, interferes with the PPD skin test used for the diagnosis of bovine tuberculosis, farmers are reluctant to use it. A sub-unit vaccine composed of immunodominant and specific antigens could offer a solution to this problem.Ninety-four M. ptb. specific antigens were identified using "in silico" comparison of M. ptb. genome with that of M. avium. Another seven M. ptb. specific antigens were identified by mass spectrometry of M. ptb. extract antigens, separated by 2D gel electrophoresis and immunoblotted with sera from diseased cattle. From these 101 candidates, 10 were selected on the basis of prediction programs for murine MHC Class I (1) and MHC Class II epitopes (2). Sequences particularly rich in potential CD8+ and CD4+ T cell epitopes were selected. These 10 candidates were cloned in the eucaryotic expression vector V1J.ns-tPA (3) and checked for expression in transiently transfected BHK cells. Immunogenicity was analyzed by plasmid DNA vaccination of BALB/c and C57BL/6 mice. M. ptb. specific Th1 type (IL-2 and IFN-γ) spleen cell cytokine secretion and antibody production was examined. Screening of the protective efficacy of these M. ptb. specific DNA vaccines is in progress.

References

1. Nussbaum AK, Kuttler C, Tenzer S, Schild H, 2003. Curr Opin Immunol 15:69.2. Feller DC, de la Cruz VF, 1991. Nature 349:720.3. Montgomery DL, Shiver JW, Leander KR, Perry HC, Friedman A, Martinez D, Ulmer JB, Donnelly JJ, Liu MA, 1993. DNA Cell Biol 12:777.

Sponsorship

Vi.R. is holder of a FRIA fellowship. R.W is Research Associate of the FNRS. This work is partially supported by the "region Wallonne" of Belgium